Abstract
Al2O3/Co composites were fabricated by vacuum hot-pressing a mixture of α-Al2O3 powder and a fine cobalt powder. Submicron-sized cobalt particles were uniformly dispersed into the Al2O3 matrix, and the dispersed type was a more inter-/intragranular one with increases of cobalt content up to 40 wt% Co addition. The growth of cobalt particles occurred with increasing cobalt content. At 50 wt% Co addition, however, the growth as well as coalescence of cobalt particles occurred. The phases formed in the Al2O3/Co composites were f-Co(fcc), h-Co(hcp), α-Al2O3, and a small amount of graphite. Significant improvements in bending strength (from 341 to 771 MPa) and fracture toughness (from 3.7 to 6.7 MPaċm1/2) of the Al2O3/40 wt% Co(23 vol% Co) composite compared to monolithic Al2O3 were achieved by dispersing submicron-sized Co particles into the Al2O3 matrix. The improvement in bending strength was attributed to the compressive thermal residual stress in the matrix Al2O3 induced by the mismatch of the coefficients of thermal expansion (CTE) between the matrix Al2O3 grains and cobalt particles during cooling from hot-pressing temperature. The fracture toughness of the composite was enhanced by crack bridging, crack deflection, and compressive thermal residual stress.
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References
C. O. Mchugh, T. J. Whalen and M. Humenik, Jr. J. Am. Ceram. Soc. 49 (1996) 486.
W. H. Tuan and R. J. Brook, J. Eur. Ceram. Soc. 6 (1990) 31.
N. Claussen, J. Steeb and R. F. Pabst, Am. Ceram. Soc. Bull. 56 (1977) 559.
C. S. Hwang, Y. J. Chang and S. W. Chen, J. Ceram. Soc. Jpn. 104 (1996) 1.
K. Niihara, J. Ceram. Soc. Jpn. 99 (1991) 974.
L. C. Stearns, J. Zhao and M. P. Harmer, J. Eur. Ceram. Soc. 10 (1992) 473.
M. Nawa, T. Sekino and K. Niihara, J. Mater. Sci. 29 (1994) 3185.
G. Pezzotti, T. Nishida and M. Sakai, J. Ceram. Soc. Jpn. 103 (1995) 901.
M. Taya, S. Hayashi, A. S. Kobayashi and H. S. Yoon, J. Am. Ceram. Soc. 73 (1990) 1382.
A. V. Virkar and D. L. Johnson, J. Am. Ceram. Soc. 60 (1977) 514.
K. T. Faber and A. G. Evans, Acta Metall. 31 (1983) 565.
K. T. Faber and A. G. Evans, Acta Metall. 31 (1983) 577.
G. C. Wei and P. F. Becher, J. Am. Ceram. Soc. 67 (1984) 571.
B. Budiansky, J. C. Amazigo and A.G. Evans, J. Mech. Phys. Solids 36 (1988) 167.
H. Suzuki, “Refractory Hard Metal and Sintered Hard Materials: Basics and Application” (Maruzen, Tokyo, 1986).
N. Claussen, J. Am. Ceram. Soc. 61 (1978) 85.
J. M. Potter and R. A. Millard, in “Advances in X-Ray Analysis,” Vol. 20, 1977, edited byH. F. Mcmurdie, C. S. Barrett, J. B. Newkirk and C. O. Ruud (Plenum Press, 1977) p. 309.
K. Niihara, Bull. Ceram. Soc. Jpn. 20 (1985) 12.
R. C. Pohanka, R. W. Rice and B. E. Walker, Jr., J. Am. Ceram. Soc. 59 (1976) 71.
G. Pezzotti, V. Sergo, K. Ota, O. Sbaizero, N. Muraki, T. Nishida and M. Sakai, J. Ceram. Soc. Jpn. 104 (1996) 497.
P. F. Becher, J. Ceram. Soc. Jpn. 99 (1991) 993.
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Tai, W.P., Watanabe, T. Preparation and mechanical properties of Al2O3 reinforced by submicrometer Co particles. Journal of Materials Science 33, 5795–5801 (1998). https://doi.org/10.1023/A:1004493830194
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DOI: https://doi.org/10.1023/A:1004493830194